A wide variety of gas sensors and gas sensor elements are used to measure different gases. More particularly, a sensor element of an exhaust gas sensor may be used in automotive applications to measure different gases (e.g., oxygen) in the exhaust gas.
Over time, however, different components in the exhaust gases tend to contaminate different parts of the gas sensor. More specifically, components such as lead, phosphorus, silicon, manganese, zinc, calcium, phosphates, oil ashes, rusts, metal oxides and other elements in the exhaust gas may tend to contaminate the electrode. More particularly, an outer electrode of the sensing element may be contaminated, and the porosity of the protective layer system may also be clogged, eventually affecting the functioning of the sensor and sometimes rendering the sensor or sensor element inoperable. Acidic exhaust components such as PxOy and SOx, wherein x and y are positive whole numbers, may also contaminate the sensor element, as well as reactive catalyst poisons such as lead, silicon and bismuth compounds. As a result, protective coatings are continually being sought in order to inhibit and/or prevent contamination of sensor elements and gas sensors.